This invention relates to the field involving the generation and display of energy time curves (ETCs) and will have special, but not limited, application to a method of correIating and displaying ETCs for the determination of acoustical characteristics in room such as a concert hall Such method including the determination and display of the ETCs' arrival time, intensity and direction for visually approximating the room's acoustical configuration.
In the musical industry, it is often desirous to determine the acoustical characteristics of a concert hall to maximize the sound of the hall so that each listener may enjoy the complete sound of the performing musicians. Such concert halls have individual characteristics and problem areas. Characteristics of such halls include reflection points i.e. where a sound at a given frequency is reflected and absorbtion points i.e. where sound at a given frequency is absorbed and not reflected. To determine such characteristics a time delay spectrometer may be used to transmit a test signal which sweeps through a desired frequency range and then receives the reflected frequencies through a microphone. Through processing, the reflected frequencies are displayed to indicate to the user general areas of specific frequency reflection or specific frequency absorption. The user then applies this information to alter the hall's physical makeup via additions of reflectors in areas of high absorption and absorbers in areas of high reflection to maximize the total sound of the hall.
Heretofore, the above mentioned method of determining the acoustical characteristics of a concert hall or similar room has used a single ETC generated by a time delay spectrometer which receives the reflected frequencies from an omni-directional microphone. This method, disclosed in U.S. Pat. Nos. 3,466,652 and 4,279,019 and in an article written by Richard C. Heyer entitled Acoustical Measurements by Time Delay Spectrometry, printed in the October 1967 issue of the Journal of the Audio Engineering Society, results in the loss of specific directional information essential to accurate acoustical measurements.